US5781328A - Electro-optical modulator - Google Patents

Electro-optical modulator Download PDF

Info

Publication number
US5781328A
US5781328A US08/693,318 US69331896A US5781328A US 5781328 A US5781328 A US 5781328A US 69331896 A US69331896 A US 69331896A US 5781328 A US5781328 A US 5781328A
Authority
US
United States
Prior art keywords
crystal
electro
modulator according
optical
light beam
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US08/693,318
Other languages
English (en)
Inventor
Jean-Paul Salvestrini
Marc Fontana
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Universite Paul Verlaine-Metz
Original Assignee
Universite Paul Verlaine-Metz
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Universite Paul Verlaine-Metz filed Critical Universite Paul Verlaine-Metz
Assigned to UNIVERSITE DE METZ reassignment UNIVERSITE DE METZ ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: FONTANA, MARC, SALVESTRINI, JEAN-PAUL
Application granted granted Critical
Publication of US5781328A publication Critical patent/US5781328A/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/0009—Materials therefor
    • G02F1/0018—Electro-optical materials
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/0009—Materials therefor
    • G02F1/0018—Electro-optical materials
    • G02F1/0027—Ferro-electric materials

Definitions

  • the invention relates to an electro-optical modulator.
  • Such devices are used for modulating light beams, that is to say for modifying their polarization, their phase, their frequency or their intensity, by modifying the medium through which they propagate, by the action of an electric field.
  • wavelength multiplexing making it possible to create a plurality of beams of different wavelength from an incident beam of given wavelength, by frequency modulation,
  • Electro-optical modulators are made either from bulk materials, in general single crystals constituting the electro-optical medium through which the light beam to be modulated passes, or from thin films or waveguides. The latter make it possible to obtain modulation in a wide frequency range (up to several gigahertz), which is very useful in telecommuniations in order to increase the data transfer rate. Such devices are of complex design and expensive.
  • modulators made from bulk crystals are widely used, in particular for intensity or phase modulation functions.
  • inorganic ferroelectrics LiNbO 3 , KNbO 3 , BaTiO 3 , which generally have high electro-optical coefficients and refractive indices. However, their dielectric permittivity is high and their production is laborious and poorly mastered.
  • the direction of the electric field applied to the electro-optical material may be orthogonal to (this case is referred to as transverse configuration) or else collinear with (this case is referred to as longitudinal configuration) the direction of propagation of the light beam.
  • L and d the dimensions of the crystal, respectively in the direction of propagation of the beam to be modulated and in the direction of the electric field.
  • L is equal to d in the case of a longitudinal configuration.
  • the high-wave voltage V.sub. ⁇ is the voltage to be applied to the crystal in order to cause a phase shift of ⁇ radians between the components of the polarization of a light beam passing through the modulator, that is to say the change from a maximum to a minimum in the intensity of the light transmitted through a suitably oriented polarizer.
  • the modulation efficiency of a light beam depends greatly on V.sub. ⁇ . It is important for this voltage V.sub. ⁇ to be as small as possible.
  • V.sub. ⁇ * 10,000 V for an ADP crystal.
  • the modulators In order to limit the value of the electric voltage applied, the modulators comprise crystals of large dimension L and small dimension d. This gives voltages V.sub. ⁇ of the order of several hundreds of volts. It nevertheless remains necessary to use a unit which amplifies the voltage applied. This leads to the electrical control device associated with the modulator being large and increases the cost of the system.
  • the electrical control power is proportional to the pass-band. It will therefore be beneficial to have a material whose half-wave voltage and dielectric permittivity are as small as possible.
  • the birefringence of the crystals used to date depends greatly on temperature, which may lead to a shift in the operating point of the modulator. This makes it necessary to install the material in a chamber which is perfectly controlled in terms of temperature and/or to compensate for the natural birefringence. This compensation may be performed by inserting into the modulator a second crystal whose dimensions are strictly identical to the first and whose orientation is such that its natural birefringence exactly cancels that of the first crystal.
  • the modulation frequency is an important parameter in the definition of the specifications of an electro-optical device.
  • the cut-off frequency of an optical communication device may actually govern the data transfer rate.
  • a modulator electro-optical crystal can be modelled to first approximation by an RC electrical circuit.
  • the value of the capacitance of a capacitor is proportional to the surface area of its electrodes. It will therefore be beneficial to use a small crystal in order for it to have a small equivalent capacitance.
  • the invention thus proposes the use in an electro-optical modulator of an electro-optical crystal in the form of a solid-solution compound of formula (NH 4 ) x Rb 1 -xH 1 - y D y SeO 4 , x and y being concentration coefficients varying from 0 to 1, in order to modify the polarization, the phase or the intensity of an incident light beam, using a small control voltage.
  • the invention also relates to an electro-optical modulator comprising:
  • the crystal is a solid-solution compound of formula (NH 4 ) x Rb 1 -xH 1 - yD y SeO 4 , x and y being concentration coefficients varying from 0 to 1.
  • the type of material envisaged in the invention for producing an electro-optical modulator has a reduced half-wave voltage V.sub. ⁇ * which can be limited to approximately 270 volts, that is to say of the order of 55 times less than for KDP and almost 37 times less than for ADP.
  • the voltage V.sub. ⁇ consequently remains small without having to use a crystal of large dimension L. This reduces the absorption losses in the crystal.
  • the fabrication (and more precisely growth) time of the crystals is also reduced.
  • the type of crystal proposed in the invention is furthermore five to twenty times less sensitive to temperature variations than most materials currently used (ADP, KDP).
  • FIG. 1 represents a first electro-optical modulator produced in accordance with the invention
  • FIG. 2 represents a second electro-optical modulator produced in accordance with the invention
  • FIG. 1 presents a first electro-optical modulator produced in accordance with the invention.
  • an L-shaped casing 2 used as a support, which allows a light beam to be modulated to pass through
  • the casing includes two plugs, one of which, having the reference numeral 4, is represented in FIG. 1. These plugs make it possible to connect two opposite faces (one of which is represented, having the reference numeral 5) of the crystal 1 to the voltage source by means of electrodes running over an insulating base 3.
  • Those faces of the crystal 1 which are connected to the voltage source will, in a conventional fashion, be covered with a metal deposit, for example of gold or silver, in order to create a uniform electric field in the volume of the crystal.
  • the crystal is oriented in such a way that the beam is normal to a plane formed by two of the crystalline axes of the crystal.
  • the beam will be normal to the plane formed by the crystalline axes a and b, and will therefore propagate along the crystalline axis c of the crystal.
  • the crystal will be a solid-solution compound of formula:
  • a larger concentration of ammonium makes it possible to widen the passband of the modulator.
  • a larger concentration of rubidium makes it possible to reduce the value of the half-wave voltage.
  • the voltage source will produce an AC voltage. It will thus be possible to produce a voltage including an AC component and a DC component.
  • the presence of a DC component is one way of compensating for the temperature drift of the modulator by shifting its operating point. In practice, it will not be necessary to produce a DC component because of the low temperature sensitivity of the type of crystal employed.
  • an amplifier will optionally be interposed between the voltage source and the crystal.
  • the crystal is formed by rubidium hydrogen selenate, it has a reduced half-wave voltage of the order of 270 volts.
  • a crystal having a dimension L of 10 millimetres and a dimension d of 2 millimetres a half-wave voltage of the order of 50 volts will be obtained. It will therefore be possible to omit the amplifier.
  • the crystal is formed by ammonium hydrogen selenate, the reduced half-wave voltage is approximately ten times higher.
  • An amplifier for the voltage produced will then preferably be interposed, thus avoiding the necessity of substantially increasing the ratio L/d of the crystal, which would increase the absorption losses in the crystal.
  • it will be possible to produce a modulator whose control voltage is limited to approximately 200 volts, that is to say much less than the voltages conventionally used.
  • the electric field will be directed substantially parallel to the ferroelectric axis of the crystal.
  • the crystal is formed from rubidium or ammonium hydrogen selenate, this will be the crystalline axis b.
  • This will make it possible to benefit from the reduced half-wave voltage V.sub. ⁇ * having the smallest value.
  • This is advantageous in so far as it will be possible to choose a crystal with smaller ratio L/d, for equal control voltage, compared to a different orientation of the electric field created. This makes the modulator more compact.
  • FIG. 2 presents a second electro-optical modulator produced in accordance with the invention.
  • a polarizer 6 placed upstream of the crystal, the axis of which is at 45° to the crystalline axes of the crystal 1 forming the input face of this crystal (that is to say the axes a and b in the example described), and in the plane of these axes.
  • the polarizer 6 is therefore conventionally positioned in the incidence plane of the beam to be modulated. Its presence makes it possible to use the modulator as a phase modulator or as a polarization modulator.
  • a second polarizer 6' the axis of which is at 90° to the first, may be placed downstream of the crystal 1 in order to use the device as an intensity modulator.
  • a quarter-wave plate 7 the fast and slow axes of which are oriented at 45° to the crystalline axes a and b, and in the same plane, may be inserted downstream of the crystal 1, between the latter and the second polarizer 6', in order to obtain a linear response of the intensity variation as a function of the phase shift introduced by the electro-optical effect.
  • the presence of one or more polarizers and of a quarter-wave plate will depend on the use of the modulator, depending on whether the desire is to modify the intensity of the light beam, its phase, its polarization, its frequency, or more than one of these characteristics simultaneously.
  • the crystal may be orientated in a different way.
  • the electric field and the direction of propagation of the light wave may be oriented differently with respect to the crystalline axes, or else not parallel to the crystalline axes of the crystal.
  • the longitudinal configuration does not make it possible to reduce the control voltage by altering the dimensions of the crystal.
  • the longitudinal configuration is more suitable for processing large-diameter light beams requiring compactness. It can be used for the generation of laser pulses. However, it requires higher electric voltages, and the modulation is therefore technologically limited to low frequencies. Furthermore, it requires transparent electrodes to be fitted.
  • the transverse configuration allows large passbands since the half-wave voltage can be reduced by increasing the propagation distance in the crystal and by reducing the inter-electrode distance. It is, however, more sensitive to temperature variations.
  • a plurality of crystals may also be arranged in series along the direction of propagation of the light beam, and oriented in such a way that their natural birefringences compensate each another.

Landscapes

  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Lasers (AREA)
US08/693,318 1994-02-17 1995-02-14 Electro-optical modulator Expired - Fee Related US5781328A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9402015 1994-02-17
FR9402015A FR2716271B1 (fr) 1994-02-17 1994-02-17 Dispositif de polarisation et de modulation électro-optique de lumière utilisant un cristal de faibles dimensions et une très basse tension de commande.
PCT/FR1995/000169 WO1995022781A1 (fr) 1994-02-17 1995-02-14 Modulateur electro-optique

Publications (1)

Publication Number Publication Date
US5781328A true US5781328A (en) 1998-07-14

Family

ID=9460324

Family Applications (1)

Application Number Title Priority Date Filing Date
US08/693,318 Expired - Fee Related US5781328A (en) 1994-02-17 1995-02-14 Electro-optical modulator

Country Status (6)

Country Link
US (1) US5781328A (de)
EP (1) EP0745232B1 (de)
AU (1) AU1814795A (de)
DE (1) DE69501320T2 (de)
FR (1) FR2716271B1 (de)
WO (1) WO1995022781A1 (de)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5157539A (en) * 1991-01-22 1992-10-20 Cleveland Crystals, Inc Multi-element electrooptic modulators with crystal axes oriented obliquely to direction of electric field

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5157539A (en) * 1991-01-22 1992-10-20 Cleveland Crystals, Inc Multi-element electrooptic modulators with crystal axes oriented obliquely to direction of electric field

Non-Patent Citations (8)

* Cited by examiner, † Cited by third party
Title
A. Waskowska et al., Ammonium Deuterium Selenate and Rubidium Deuterium Selenate , ACTA Crystallographica, vol. B38, 1982, pp. 2017 2020. *
A. Waskowska et al., Ammonium Deuterium Selenate and Rubidium Deuterium Selenate, ACTA Crystallographica, vol. B38, 1982, pp. 2017-2020.
J. Salvestrini et al., New Material With Strong Electro Optic Effect: Rubidium Hydrogen Selenate ( RbHSeO 4 ), Applied Physics Letters, vol. 64, No. 15, Apr. 1994, pp. 1920 1922. *
J. Salvestrini et al., New Material With Strong Electro-Optic Effect: Rubidium Hydrogen Selenate (RbHSeO4), Applied Physics Letters, vol. 64, No. 15, Apr. 1994, pp. 1920-1922.
R. Popranski et al., Specific Heat of Hydrogen Selenate Crystals , Ferroelectrics, vol. 79, 1988, pp. 245 248. *
R. Popranski et al., Specific Heat of Hydrogen Selenate Crystals, Ferroelectrics, vol. 79, 1988, pp. 245-248.
T. Tsukamoto et al., Deflection of Light Induced by Ferroelectric ferroelastic Crystals ,Japanese Journal of Applied Physics, Supplement 24 3, vol. 24 (1985), pp. 165 168. *
T. Tsukamoto et al., Deflection of Light Induced by Ferroelectric-ferroelastic Crystals,Japanese Journal of Applied Physics, Supplement 24-3, vol. 24 (1985), pp. 165-168.

Also Published As

Publication number Publication date
FR2716271B1 (fr) 1996-05-03
WO1995022781A1 (fr) 1995-08-24
DE69501320D1 (de) 1998-02-05
EP0745232A1 (de) 1996-12-04
AU1814795A (en) 1995-09-04
DE69501320T2 (de) 1998-07-23
EP0745232B1 (de) 1997-12-29
FR2716271A1 (fr) 1995-08-18

Similar Documents

Publication Publication Date Title
US3874782A (en) Light-guiding switch, modulator and deflector employing antisotropic substrate
US4583817A (en) Non-linear integrated optical coupler and parametric oscillator incorporating such a coupler
US3679288A (en) Tunable acousto-optic method and apparatus
US5159487A (en) Optical parametric oscillator OPO having a variable line narrowed output
Hirabayashi et al. Liquid crystal devices for optical communication and information processing systems
US4229079A (en) Electro-optic modulator with improved acousto-optic suppression, heat transfer and mechanical support
EP0375768B1 (de) Optisches lichtventilsystem zur erzeugung eines phasenkonjugierten strahls steuerbarer intensität
CN103730826A (zh) 一种可调谐激光器系统
US3799659A (en) TL{11 AsS{11 {11 CRYSTALS AND ACOUSTO-OPTICAL SYSTEMS
US4607909A (en) Method for modulating a carrier wave
US4359268A (en) Light quantity control apparatus
US5002360A (en) Frequency doubling optical waveguide with active phase matching
EP1255156A2 (de) Abstimmbarer optischer Filter
US6584260B2 (en) Electro-optical device and a wavelength selection method utilizing the same
US4582397A (en) Diospersive acousto-optic filter
US5781328A (en) Electro-optical modulator
US3900246A (en) Lanthanum titanate single crystal electro-optic modulator
US3915556A (en) Tl{hd 3{b AsS{HD 4 {B crystals and acousto-optical systems
EP0431698B1 (de) Frequenzverdoppelnder optischer Wellenleiter mit aktiver Phasenanpassung und Frequenzverdoppelungssystem
JPH01147528A (ja) ２次高調波光発生素子
JPH06148692A (ja) 波長可変液晶光フィルタ
CN111913308A (zh) 利用温度控制ktn包层波导传输模式的系统及调制方法
US3625592A (en) Electro-optical modulator
JPS5928894B2 (ja) 電気光学光変調器
JPS6150288B2 (de)

Legal Events

Date Code Title Description
AS Assignment

Owner name: UNIVERSITE DE METZ, FRANCE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SALVESTRINI, JEAN-PAUL;FONTANA, MARC;REEL/FRAME:008731/0882

Effective date: 19960823

REMI Maintenance fee reminder mailed
LAPS Lapse for failure to pay maintenance fees
STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Lapsed due to failure to pay maintenance fee

Effective date: 20020714